A Disjointed Pathway for Malonate Degradation by Rhodopseudomonas palustris

ABSTRACT The purple nonsulfur phototrophic bacterium Rhodopseudomonas palustris strain CGA009 uses the three-carbon dicarboxylic acid malonate as the sole carbon source under phototrophic conditions. However, this bacterium grows extremely slowly on this compound and does not have operons for the two pathways for malonate degradation that have been detected in other bacteria. Many bacteria grow on a spectrum of carbon sources, some of which are classified as poor growth substrates because they support low growth rates. This trait is rarely addressed in the literature, but slow growth is potentially useful in biotechnological applications where it is imperative for bacteria to divert cellular resources to value-added products rather than to growth. This prompted us to explore the genetic and physiological basis for the slow growth of R. palustris with malonate as a carbon source. There are two unlinked genes annotated as encoding a malonyl coenzyme A (malonyl-CoA) synthetase (MatB) and a malonyl-CoA decarboxylase (MatA) in the genome of R. palustris, which we verified as having the predicted functions. Additionally, two tripartite ATP-independent periplasmic transporters (TRAP systems) encoded by rpa2047 to rpa2049 and rpa2541 to rpa2543 were needed for optimal growth on malonate. Most of these genes were expressed constitutively during growth on several carbon sources, including malonate. Our data indicate that R. palustris uses a piecemeal approach to growing on malonate. The data also raise the possibility that this bacterium will evolve to use malonate efficiently if confronted with an appropriate selection pressure. IMPORTANCE There is interest in understanding how bacteria metabolize malonate because this three-carbon dicarboxylic acid can serve as a building block in bioengineering applications to generate useful compounds that have an odd number of carbons. We found that the phototrophic bacterium Rhodopseudomonas palustris grows extremely slowly on malonate. We identified two enzymes and two TRAP transporters involved in the uptake and metabolism of malonate, but some of these elements are apparently not very efficient. R. palustris cells growing with malonate have the potential to be excellent biocatalysts, because cells would be able to divert cellular resources to the production of value-added compounds instead of using them to support rapid growth. In addition, our results suggest that R. palustris is a candidate for directed evolution studies to improve growth on malonate and to observe the kinds of genetic adaptations that occur to make a metabolic pathway operate more efficiently.

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The Cyclic AMP Receptor Protein Regulates Quorum Sensing and Global Gene Expression in Yersinia pestis during Planktonic Growth and Growth in Biofilms

mBio ◽

10.1128/mbio.02613-19 ◽

2019 ◽

Vol 10 (6) ◽

Cited By ~ 6

Author(s):

Jeremy T. Ritzert ◽

George Minasov ◽

Ryan Embry ◽

Matthew J. Schipma ◽

Karla J. F. Satchell

Keyword(s):

Gene Expression ◽

Quorum Sensing ◽

Carbon Source ◽

Cyclic Amp ◽

Yersinia Pestis ◽

Carbon Sources ◽

Transcriptional Regulator ◽

Receptor Protein ◽

Content Type ◽

Bacterial Physiology

ABSTRACT Cyclic AMP (cAMP) receptor protein (Crp) is an important transcriptional regulator of Yersinia pestis. Expression of crp increases during pneumonic plague as the pathogen depletes glucose and forms large biofilms within lungs. To better understand control of Y. pestis Crp, we determined a 1.8-Å crystal structure of the protein-cAMP complex. We found that compared to Escherichia coli Crp, C helix amino acid substitutions in Y. pestis Crp did not impact the cAMP dependency of Crp to bind DNA promoters. To investigate Y. pestis Crp-regulated genes during plague pneumonia, we performed RNA sequencing on both wild-type and Δcrp mutant bacteria growing in planktonic and biofilm states in minimal media with glucose or glycerol. Y. pestis Crp was found to dramatically alter expression of hundreds of genes in a manner dependent upon carbon source and growth state. Gel shift assays confirmed direct regulation of the malT and ptsG promoters, and Crp was then linked to Y. pestis growth on maltose as a sole carbon source. Iron regulation genes ybtA and fyuA were found to be indirectly regulated by Crp. A new connection between carbon source and quorum sensing was revealed as Crp was found to regulate production of acyl-homoserine lactones (AHLs) through direct and indirect regulation of genes for AHL synthetases and receptors. AHLs were subsequently identified in the lungs of Y. pestis-infected mice when crp expression was highest in Y. pestis biofilms. Thus, in addition to the well-studied pla gene, other Crp-regulated genes likely have important functions during plague infection. IMPORTANCE Bacterial pathogens have evolved extensive signaling pathways to translate environmental signals into changes in gene expression. While Crp has long been appreciated for its role in regulating metabolism of carbon sources in many bacterial species, transcriptional profiling has revealed that this protein regulates many other aspects of bacterial physiology. The plague pathogen Y. pestis requires this global regulator to survive in blood, skin, and lungs. During disease progression, this organism adapts to changes within these niches. In addition to regulating genes for metabolism of nonglucose sugars, we found that Crp regulates genes for virulence, metal acquisition, and quorum sensing by direct or indirect mechanisms. Thus, this single transcriptional regulator, which responds to changes in available carbon sources, can regulate multiple critical behaviors for causing disease.

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The Catabolite Repressor/Activator Cra Is a Bridge Connecting Carbon Metabolism and Host Colonization in the Plant Drought Resistance-Promoting Bacterium Pantoea alhagi LTYR-11Z

Applied and Environmental Microbiology ◽

10.1128/aem.00054-18 ◽

2018 ◽

Vol 84 (13) ◽

Cited By ~ 3

Author(s):

Lei Zhang ◽

Muhang Li ◽

Qiqi Li ◽

Chaoqiong Chen ◽

Meng Qu ◽

...

Keyword(s):

Carbon Source ◽

Carbon Metabolism ◽

Carbon Sources ◽

Endophytic Bacterium ◽

Bacterial Attachment ◽

Gene Encoding ◽

Wheat Roots ◽

Host Colonization ◽

Content Type

ABSTRACT Efficient root colonization is a prerequisite for application of plant growth-promoting (PGP) bacteria in improving health and yield of agricultural crops. We have recently identified an endophytic bacterium, Pantoea alhagi LTYR-11Z, with multiple PGP properties that effectively colonizes the root system of wheat and improves its growth and drought tolerance. To identify novel regulatory genes required for wheat colonization, we screened an LTYR-11Z transposon (Tn) insertion library and found cra to be a colonization-related gene. By using transcriptome (RNA-seq) analysis, we found that transcriptional levels of an eps operon, the ydiV gene encoding an anti-FlhD 4 C 2 factor, and the yedQ gene encoding an enzyme for synthesis of cyclic dimeric GMP (c-di-GMP) were significantly downregulated in the Δ cra mutant. Further studies demonstrated that Cra directly binds to the promoters of the eps operon, ydiV , and yedQ and activates their expression, thus inhibiting motility and promoting exopolysaccharide (EPS) production and biofilm formation. Consistent with previous findings that Cra plays a role in transcriptional regulation in response to carbon source availability, the activating effects of Cra were much more pronounced when LTYR-11Z was grown within a gluconeogenic environment than when it was grown within a glycolytic environment. We further demonstrate that the ability of LTYR-11Z to colonize wheat roots is modulated by the availability of carbon sources. Altogether, these results uncover a novel strategy utilized by LTYR-11Z to achieve host colonization in response to carbon nutrition in the environment, in which Cra bridges a connection between carbon metabolism and colonization capacity of LTYR-11Z. IMPORTANCE Rapid and appropriate response to environmental signals is crucial for bacteria to adapt to competitive environments and to establish interactions with their hosts. Efficient colonization and persistence within the host are controlled by various regulatory factors that respond to specific environmental cues. The most common is nutrient availability. In this work, we unraveled the pivotal role of Cra in regulation of colonization ability of Pantoea alhagi LTYR-11Z in response to carbon source availability. Moreover, we identified three novel members of the Cra regulon involved in EPS synthesis, regulation of flagellar biosynthesis, and synthesis of c-di-GMP and propose a working model to explain the Cra-mediated regulatory mechanism that links carbon metabolism to host colonization. This study elucidates the regulatory role of Cra in bacterial attachment and colonization of plants, which raises the possibility of extending our studies to other bacteria associated with plant and human health.

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Metabolic and Developmental Effects Resulting from Deletion of the citA Gene Encoding Citrate Synthase in Aspergillus nidulans

Eukaryotic Cell ◽

10.1128/ec.00373-09 ◽

2010 ◽

Vol 9 (4) ◽

pp. 656-666 ◽

Cited By ~ 9

Author(s):

Sandra L. Murray ◽

Michael J. Hynes

Keyword(s):

Aspergillus Nidulans ◽

Fluorescent Protein ◽

Citrate Synthase ◽

Glyoxylate Cycle ◽

Single Gene ◽

Carbon Sources ◽

Tca Cycle ◽

Poor Growth ◽

Content Type ◽

The Glyoxylate Cycle

ABSTRACT Citrate synthase is a central activity in carbon metabolism. It is required for the tricarboxylic acid (TCA) cycle, respiration, and the glyoxylate cycle. In Saccharomyces cerevisiae and Arabidopsis thaliana, there are mitochondrial and peroxisomal isoforms encoded by separate genes, while in Aspergillus nidulans, a single gene, citA, encodes a protein with predicted mitochondrial and peroxisomal targeting sequences (PTS). Deletion of citA results in poor growth on glucose but not on derepressing carbon sources, including those requiring the glyoxylate cycle. Growth on glucose is restored by a mutation in the creA carbon catabolite repressor gene. Methylcitrate synthase, required for propionyl-coenzyme A (CoA) metabolism, has previously been shown to have citrate synthase activity. We have been unable to construct the mcsAΔ citAΔ double mutant, and the expression of mcsA is subject to CreA-mediated carbon repression. Therefore, McsA can substitute for the loss of CitA activity. Deletion of citA does not affect conidiation or sexual development but results in delayed conidial germination as well as a complete loss of ascospores in fruiting bodies, which can be attributed to loss of meiosis. These defects are suppressed by the creA204 mutation, indicating that McsA activity can substitute for the loss of CitA. A mutation of the putative PTS1-encoding sequence in citA had no effect on carbon source utilization or development but did result in slower colony extension arising from single conidia or ascospores. CitA-green fluorescent protein (GFP) studies showed mitochondrial localization in conidia, ascospores, and hyphae. Peroxisomal localization was not detected. However, a very low and variable detection of punctate GFP fluorescence was sometimes observed in conidia germinated for 5 h when the mitochondrial targeting sequence was deleted.

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Sodium Lactate Negatively Regulates Shewanella putrefaciens CN32 Biofilm Formation via a Three-Component Regulatory System (LrbS-LrbA-LrbR)

Applied and Environmental Microbiology ◽

10.1128/aem.00712-17 ◽

2017 ◽

Vol 83 (14) ◽

Cited By ~ 4

Author(s):

Cong Liu ◽

Jinshui Yang ◽

Liang Liu ◽

Baozhen Li ◽

Hongli Yuan ◽

...

Keyword(s):

Carbon Source ◽

Biofilm Formation ◽

Present Report ◽

Carbon Sources ◽

Regulatory System ◽

Shewanella Putrefaciens ◽

Sodium Lactate ◽

Signal Molecule ◽

Content Type ◽

Biofilm Development

ABSTRACT The capability of biofilm formation has a major impact on the industrial and biotechnological applications of Shewanella putrefaciens CN32. However, the detailed regulatory mechanisms underlying biofilm formation in this strain remain largely unknown. In the present report, we describe a three-component regulatory system which negatively regulates the biofilm formation of S. putrefaciens CN32. This system consists of a histidine kinase LrbS (Sputcn32_0303) and two cognate response regulators, including a transcription factor, LrbA (Sputcn32_0304), and a phosphodiesterase, LrbR (Sputcn32_0305). LrbS responds to the signal of the carbon source sodium lactate and subsequently activates LrbA. The activated LrbA then promotes the expression of lrbR, the gene for the other response regulator. The bis-(3′-5′)-cyclic dimeric GMP (c-di-GMP) phosphodiesterase LrbR, containing an EAL domain, decreases the concentration of intracellular c-di-GMP, thereby negatively regulating biofilm formation. In summary, the carbon source sodium lactate acts as a signal molecule that regulates biofilm formation via a three-component regulatory system (LrbS-LrbA-LrbR) in S. putrefaciens CN32. IMPORTANCE Biofilm formation is a significant capability used by some bacteria to survive in adverse environments. Numerous environmental factors can affect biofilm formation through different signal transduction pathways. Carbon sources are critical nutrients for bacterial growth, and their concentrations and types significantly influence the biomass and structure of biofilms. However, knowledge about the underlying mechanism of biofilm formation regulation by carbon source is still limited. This work elucidates a modulation pattern of biofilm formation negatively regulated by sodium lactate as a carbon source via a three-component regulatory system in S. putrefaciens CN32, which may serve as a good example for studying how the carbon sources impact biofilm development in other bacteria.

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Effects of Carbon Source and Explant Type on Somatic Embryogenesis of Four Cacao Genotypes

HortScience ◽

10.21273/hortsci.41.3.753 ◽

2006 ◽

Vol 41 (3) ◽

pp. 753-758 ◽

Cited By ~ 9

Author(s):

Abdoulaye Traore ◽

Mark J. Guiltinan

Keyword(s):

Somatic Embryogenesis ◽

Carbon Source ◽

Somatic Embryos ◽

Slow Growth ◽

Carbon Sources ◽

The Other ◽

Root Production ◽

Explant Type ◽

Embryo Maturation ◽

Genotypic Effect

The effects of five carbon sources (glucose, fructose, maltose, sorbitol, and sucrose) and two explant types (petals and staminodes) on cacao somatic embryogenesis was studied. No growth was observed on both types of explants cultured on sorbitol containing media and slow growth was obtained on media supplemented with maltose. Depending on the genotype, the percentage of explants producing one or more embryos ranged from 6% to 99%, 18% to 98%, and 3% to 82% on media containing glucose, fructose and sucrose respectively. Explants cultured continuously on maltose or sorbitol-containing media failed to produce embryos. Staminode explants produced 3 to 10 times more somatic embryos than petals. A strong genotypic effect on somatic embryogenesis was observed. Staminode explants of the Forastero clones Laranja and PSUSca 6 produced 2 to 30 times more somatic embryos than the Trinitarios UF 613 and ICS 16. During embryo maturation and conversion, no significant differences were observed among glucose, fructose, maltose, or sucrose for embryo weight, total shoot and root production. However, we found that all plantlets produced on glucose had shoots with normal cacao leaves while the other carbon sources sometimes produced plantlets with cotyledon-like leaves.

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A kinetic model of the central carbon metabolism for acrylic acid production in Escherichia coli

10.1101/2020.05.13.093294 ◽

2020 ◽

Author(s):

Alexandre Oliveira ◽

Joana Rodrigues ◽

Eugénio Ferreira ◽

Lígia Rodrigues ◽

Oscar Dias

Keyword(s):

Escherichia Coli ◽

Carbon Source ◽

Acrylic Acid ◽

Value Added ◽

Central Carbon Metabolism ◽

Industrial Scale ◽

Scale Production ◽

Malonyl Coa ◽

Glycerol 3 Phosphate Dehydrogenase ◽

Industrial Scale Production

AbstractAcrylic acid is a value-added chemical used in industry to produce diapers, coatings, paints, and adhesives, among many others. Due to its economic importance, there is currently a need for new and sustainable ways to synthesise it. Recently, the focus has been laid in the use of Escherichia coli to express the full bio-based pathway using 3-hydroxypropionate as an intermediary through three distinct pathways (glycerol, malonyl-CoA, and β-alanine). Hence, the goals of this work were to use COPASI software to assess which of the three pathways has a higher potential for industrial-scale production, from either glucose or glycerol, and identify potential targets to improve the biosynthetic pathways yields.When compared to the available literature, the models developed during this work successfully predict the production of 3-hydroxypropionate, using glycerol as carbon source in the glycerol pathway, and using glucose as a carbon source in the malonyl-CoA and β-alanine pathways. Finally, this work allowed to identify four potential over-expression targets (glycerol-3-phosphate dehydrogenase (G3pD), acetyl-CoA carboxylase (AccC), aspartate aminotransferase (AspAT), and aspartate carboxylase (AspC)) that should, theoretically, result in higher AA yields.Author summaryAcrylic acid is an economically important chemical compound due to its high market value. Nevertheless, the majority of acrylic acid consumed worldwide its produced from petroleum derivatives by a purely chemical process, which is not only expensive, but it also contributes towards environment deterioration. Hence, justifying the current need for sustainable novel production methods that allow higher profit margins. Ideally, to minimise production cust, the pathway should consist in the direct bio-based production from microbial feedstocks, such as Escherichia coli, but the current yields achieved are still to low to compete with conventional method. In this work, even though the glycerol pathway presented higher yields, we identified the malonyl-CoA route, when using glucose as carbon source, as having the most potential for industrial-scale production, since it is cheaper to implement. Furthermore, we also identified potential optimisation targets for all the tested pathways, that can help the bio-based method to compete with the conventional process.

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Complete Genome Sequence of Rhodopseudomonas palustris RCB100, an Anoxygenic Phototroph That Degrades 3-Chlorobenzoate

Microbiology Resource Announcements ◽

10.1128/mra.00043-21 ◽

2021 ◽

Vol 10 (15) ◽

Author(s):

Irshad UI Haq ◽

Kathryn R. Fixen

Keyword(s):

Carbon Source ◽

Genome Sequence ◽

Complete Genome Sequence ◽

Complete Genome ◽

Rhodopseudomonas Palustris ◽

Content Type ◽

Purple Nonsulfur Bacterium ◽

Insight Into

ABSTRACT The purple nonsulfur bacterium Rhodopseudomonas palustris RCB100 anaerobically degrades 3-chlorobenzoate (3-CBA), a halogenated pollutant. R. palustris RCB100 uses 3-CBA as a carbon source, while most R. palustris strains cannot. We report the complete genome sequence of strain RCB100 to help gain insight into how this bacterium degrades 3-CBA.

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Genetically Modified Strains of Ralstonia eutropha H16 with β-Ketothiolase Gene Deletions for Production of Copolyesters with Defined 3-Hydroxyvaleric Acid Contents

Applied and Environmental Microbiology ◽

10.1128/aem.00824-12 ◽

2012 ◽

Vol 78 (15) ◽

pp. 5375-5383 ◽

Cited By ~ 13

Author(s):

Nicole Lindenkamp ◽

Elena Volodina ◽

Alexander Steinbüchel

Keyword(s):

Fatty Acids ◽

Carbon Source ◽

Sole Carbon Source ◽

Ralstonia Eutropha ◽

Carbon Sources ◽

Production Capacity ◽

Wild Type ◽

Content Type ◽

Storage Behavior ◽

Copolymer Poly

ABSTRACTβ-Ketothiolases catalyze the first step of poly(3-hydroxybutyrate) [poly(3HB)] biosynthesis in bacteria by condensation of two acetyl coenzyme A (acetyl-CoA) molecules to acetoacetyl-CoA and also take part in the degradation of fatty acids. During growth on propionate or valerate,Ralstonia eutrophaH16 produces the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [poly(3HB-co-3HV)]. InR. eutropha, 15 β-ketothiolase homologues exist. The synthesis of 3-hydroxybutyryl-CoA (3HB-CoA) could be significantly reduced in an 8-fold mutant (Lindenkamp et al., Appl. Environ. Microbiol. 76:5373–5382, 2010). In this study, a 9-fold mutant deficient in nine β-ketothiolase gene homologues (phaA,bktB, H16_A1713, H16_B1771, H16_A1528, H16_B0381, H16_B1369, H16_A0170, andpcaF) was generated. In order to examine the polyhydroxyalkanoate production capacity when short- or long-chain and even- or odd-chain-length fatty acids were provided as carbon sources, the growth and storage behavior of several mutants from the previous study and the newly generated 9-fold mutant were analyzed. Propionate, valerate, octanoate, undecanoic acid, or oleate was chosen as the sole carbon source. On octanoate, no significant differences in growth or storage behavior were observed between wild-typeR. eutrophaand the mutants. In contrast, during the growth on oleate of a multiple mutant lackingphaA,bktB, and H16_A0170, diminished poly(3HB) accumulation occurred. Surprisingly, the amount of accumulated poly(3HB) in the multiple mutants grown on gluconate differed; it was much lower than that on oleate. The β-ketothiolase activity toward acetoacetyl-CoA in H16ΔphaAand all the multiple mutants remained 10-fold lower than the activity of the wild type, regardless of which carbon source, oleate or gluconate, was employed. During growth on valerate as a sole carbon source, the 9-fold mutant accumulated almost a poly(3-hydroxyvalerate) [poly(3HV)] homopolyester with 99 mol% 3HV constituents.

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Interactions between Bifidobacterium and Bacteroides Species in Cofermentations Are Affected by Carbon Sources, Including Exopolysaccharides Produced by Bifidobacteria

Applied and Environmental Microbiology ◽

10.1128/aem.02545-13 ◽

2013 ◽

Vol 79 (23) ◽

pp. 7518-7524 ◽

Cited By ~ 47

Author(s):

David Rios-Covian ◽

Silvia Arboleya ◽

Ana M. Hernandez-Barranco ◽

Jorge R. Alvarez-Buylla ◽

Patricia Ruas-Madiedo ◽

...

Keyword(s):

Bifidobacterium Longum ◽

Carbon Sources ◽

Short Chain Fatty Acids ◽

Poor Growth ◽

Content Type ◽

Complex Carbohydrates ◽

Fermentable Carbohydrates ◽

Specific Species ◽

The Relationship ◽

Late Stages

ABSTRACTCocultures of strains from twoBifidobacteriumand twoBacteroidesspecies were performed with exopolysaccharides (EPS) previously purified from bifidobacteria, with inulin, or with glucose as the carbon source.Bifidobacterium longumNB667 andBifidobacterium breveIPLA20004 grew in glucose but showed poor or no growth in complex carbohydrates (inulin, EPS E44, and EPS R1), whereasBacteroidesgrew well in the four carbon sources tested. In the presence of glucose, the growth ofBacteroides thetaiotaomicronDSM-2079 was inhibited byB. breve, whereas it remained unaffected in the presence ofB. longum.Ba. fragilisDSM-2151 contributed to a greater survival ofB. longum, promoting changes in the synthesis of short-chain fatty acids (SCFA) and organic acids in coculture with respect to monocultures. In complex carbohydrates, cocultures of bifidobacterium strains withBa. thetaiotaomicrondid not modify the behavior ofBacteroidesnor improve the poor growth of bifidobacteria. The metabolic activity ofBa. fragilisin coculture with bifidobacteria was not affected by EPS, but greater survival of bifidobacteria at late stages of incubation occurred in cocultures than in monocultures, leading to a higher production of acetic acid than in monocultures. Therefore, cocultures ofBifidobacteriumandBacteroidescan behave differently against fermentable carbohydrates as a function of the specific characteristics of the strains from each species. These results stress the importance of considering specific species and strain interactions and not simply higher taxonomic divisions in the relationship among intestinal microbial populations and their different responses to probiotics and prebiotics.

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Phototrophic Lactate Utilization byRhodopseudomonas palustrisIs Stimulated by Coutilization with Additional Substrates

Applied and Environmental Microbiology ◽

10.1128/aem.00048-19 ◽

2019 ◽

Vol 85 (11) ◽

Cited By ~ 3

Author(s):

Alekhya Govindaraju ◽

James B. McKinlay ◽

Breah LaSarre

Keyword(s):

Carbon Source ◽

Organic Acids ◽

Rhodopseudomonas Palustris ◽

Practical Importance ◽

Substrate Utilization ◽

Mixed Substrate ◽

Content Type ◽

Bacterial Physiology ◽

Carbon Substrates ◽

Lactate Utilization

ABSTRACTThe phototrophic purple nonsulfur bacteriumRhodopseudomonas palustrisis known for its metabolic versatility and is of interest for various industrial and environmental applications. Despite decades of research onR. palustrisgrowth under diverse conditions, patterns ofR. palustrisgrowth and carbon utilization with mixtures of carbon substrates remain largely unknown.R. palustrisreadily utilizes most short-chain organic acids but cannot readily use lactate as a sole carbon source. Here we investigated the influence of mixed-substrate utilization on phototrophic lactate consumption byR. palustris. We found that lactate was simultaneously utilized with a variety of other organic acids and glycerol in time frames that were insufficient forR. palustrisgrowth on lactate alone. Thus, lactate utilization byR. palustriswas expedited by its coutilization with additional substrates. Separately, experiments using carbon pairs that did not contain lactate revealed acetate-mediated inhibition of glycerol utilization inR. palustris. This inhibition was specific to the acetate-glycerol pair, asR. palustrissimultaneously utilized acetate or glycerol when either was paired with succinate or lactate. Overall, our results demonstrate that (i)R. palustriscommonly employs simultaneous mixed-substrate utilization, (ii) mixed-substrate utilization expands the spectrum of readily utilized organic acids in this species, and (iii)R. palustrishas the capacity to exert carbon catabolite control in a substrate-specific manner.IMPORTANCEBacterial carbon source utilization is frequently assessed using cultures provided single carbon sources. However, the utilization of carbon mixtures by bacteria (i.e., mixed-substrate utilization) is of both fundamental and practical importance; it is central to bacterial physiology and ecology, and it influences the utility of bacteria as biotechnology. Here we investigated mixed-substrate utilization by the model organismRhodopseudomonas palustris. Using mixtures of organic acids and glycerol, we show thatR. palustrisexhibits an expanded range of usable carbon substrates when provided substrates in mixtures. Specifically, coutilization enabled the prompt consumption of lactate, a substrate that is otherwise not readily used byR. palustris. Additionally, we found thatR. palustrisutilizes acetate and glycerol sequentially, revealing that this species has the capacity to use some substrates in a preferential order. These results provide insights intoR. palustrisphysiology that will aid the use ofR. palustrisfor industrial and commercial applications.

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